The invention relates to a catadioptric projection objective for microlithography for imaging an object field in an object plane onto an image field in an image plane comprising three partial objectives, as well as to a projection exposure apparatus for microlithography comprising an illumination system for providing at least one illumination mode and a catadioptric projection objective for imaging an object field in an object plane onto an image field in an image plane comprising three partial objectives, and also to a method for operating a projection exposure apparatus for microlithography comprising an illumination system for providing at least one illumination mode and a catadioptric projection objective for imaging an object field in an object plane onto an image field in an image plane comprising three partial objectives.
The object field is imaged onto a first real intermediate image by the first partial objective of the catadioptric projection objective, the first intermediate image is imaged onto a second real intermediate image by the second partial objective, and the second intermediate image is finally imaged onto the image field in the image plane by the third partial objective. The second partial objective is a catadioptric objective having exactly one concave mirror and at least one lens. Moreover, the catadioptric projection objective has two folding mirrors, wherein the first folding mirror deflects the projection light coming from the object plane in the direction of the concave mirror of the second partial objective and the second folding mirror deflects the projection light coming from the concave mirror of the second partial objective in the direction of the image plane. The projection objective has exactly two real intermediate images and a numerical aperture of greater than 1.0 in the image plane.
Catadioptric projection objectives of this type are known for example from US 2009/0034061 and from US2005/0248856.